Leather product and method for making same



March 1957 L. J. STROBINO 2,785,086

LEATHER PRODUCT AND METHOD FOR MAKING SAME Filed May 1, 1953 I I I E l 7 I 2 u I I I l I p 1 1 I v I I 5 1 t l I ll/ INVENTOR ATTORNEYS United States Patent LEATHER PRODUCT AND METHOD FOR MAKING SAME Louis J. Strobino, Utica, l Y.

Application May 1, 1953, Serial No. 352,497

9 Claims. (Cl. 117-65) This invention relates to improvements in the processing of leatherdesigned to be used in the manufacture of flexible protective shields and the like, and to the leather product so obtained. 7

In my prior Patent No. 2,367,446 there is disclosed a method of treating leather skins to decrease their heat conductivity and to increase their resistance to the destructive effects of relatively high temperatures, the leather so treated being usefully employed in various articles such as, for example, work gloves, to protect the hands of workmen engaged in occupations which require exposure of the hands to high temperature objects or conditions.

In accordance with the method there disclosed, tanned leather skins are impregnated with solid particles of a substance which is a poor conductor of heat, as for example, diatomaceous earth, lamp black, or the like. Such material, in finely divided form, as for example, such as to pass through a screen of 600jmesh, more or less, is suspended in water, and the skins tumbled therein in any suitable type of apparatus, until the particles have worked intothe pores of the skins. The skins may then be washed and dried and the fatliquoring and other usual steps taken in the manner of tanners, following which they may be formed into gloves, aprons or other articles, adapted for use as protective shields.

When leather skins are impregnated with finely divided material, as described, the nature and close propinquity of the particles within the pores of the skins makes them as a whole substantially opaque to heat rays and, in addition, increases their resistance to heat so that they will withstand relatively high temperatures for short intervals of time, without impairment.

It has now been found that a further improvement in the heat resisting and heat insulating properties of leather skins may be obtained if they are first treated in the manner briefly described hereinabove, and more fully described in my prior patent, and are then subjected to heat under conditions of temperature and time so controlled as to produce the maximum shrinkage of the leather without appreciable impairment of the hardness, tensile strength, and other desirable characteristics thereof. The method of treatment herein contemplated is applied to a split type of leather, as contrasted to a grain leather, and the conditions of temperature and time must be controlled within fairly critical limits to obtain the desired results, without impairment of the leather.

In carrying out the method in accordance with the invention, leather skins, which have previously been tanned in any suitable manner, are first impregnated with finely divided material, following which they are subjected to heat under controlled conditions of temperature and time. impregnation of the skins may be carried out in any suitable apparatus, such as that disclosed in my prior patent, and the procedure followed may be substantially similar in all respects. The heat treatment may also be carried out in any suitable type of apparatus,

one form of apparatus suitable for the purpose being shown in the accompanying drawing wherein:

Figure l is a diagrammatic view of the apparatus, a portion thereof being shown in section; and

Figure 2 is a cross-sectional view of a portion of the apparatus taken on the line 2-2 of Figure 1.

Referring to the drawing, the numeral 10 designates an oven through which heated air is continuously circulated in a closed circuit by a pump or blower 11. The pump 11 withdraws air from one end of the oven and forces it through a heater 12 into the opposite end of the oven. The heater 12 may desirably be thermostatically controlled to maintain the air passing through the oven at a predetermined temperature.

A rack 13 is slidably mounted in the oven on supporting members 14, secured to the end walls 15 of the oven adjacent the upper portions thereof. The rack 13 may desirably be made up of a plurality of rods 16, secured in spaced apart substantially parallel relation by end members 17, and reinforced, if desired, by intermediate cross-members. The end members 17 rest on the supporting members 14 and are adapted to slide therealong to permit the rack to be removed from, and inserted into, the oven through a hinged door 18.

Leather skins 19 may be supported by the rack 13 in any suitable manner as by clamps 20, suspended from the rods 16 by hooks 21 and having releasable spring pressed jaws 22 at their lower ends to grip the upper edges of the skins. The skins hang freely downward in the oven and are arranged longitudinally thereof in spaced apart relation so that the heated air flows therebetween as it passes through the oven.

The apparatus may be operated either intermittently or continuously. In the intermittent operation of the apparatus the blower 11 is stopped after the skins in the oven have been subjected to the desired heat treatment. The rack 13 and the treated skins are then removed from the oven through the door 18, and a new batch of skins, which has previously been attached to a separate rack 13, is then inserted into the oven. Operation of the blower 11 is then started and the cycle repeated for each separate batch of skins. Any suitable type of timing mechanism may be utilized to stop the blower 11 when the required heat treatment has been completed.

In the continuous operation of the apparatus the blower 11 continues to operate while the treated batch of skins is being removed and replaced by an untreated batch. In such event any suitable type of signal may be employed to indicate when the treatment has been completed.

It will be appreciated, of course, that the apparatus herein shown is merely illustrative of one practical way of carrying out the method. Variations in this apparatus, or other forms of apparatus suitable for the purpose, will readily suggest themselves to persons skilled in the art, one such variation involving the use of a suitable mechanism, such as an endless conveyor, for continuously moving the skins through the oven at a speed calculated to give the desired heat treatment.

As previously indicated herein, the temperature and time of treatment of the leather must be controlled within rather critical limits. Thus I have found that the temperature should be maintained within the range from about 350 F. to about 400 F. and the time within the range from about three minutes to about 15 minutes. The particular temperature and time of treatment will depend on the type of leather, the type and degree of impregnation, the thickness of the leather, and other factors. It has been found that the conditions of treatment, herein disclosed, result in shrinkage of the skins to the optimum degree for heat insulating and heat resisting qualities of the leather, as well as wearing qualities, when the leather is formed into an article, such as 3 aglove. The degree of shrinkage will range from about to about 40% of the original area of the skin, and will usually be in the neighborhood of about 30%.

'Leather treated in accordance with the method of the invention has an increased resistance to the passage of heat therethrough and, in addition, withstands temperatures of the order of 600 to 800 F. and higher for short periods of time without impairment. For example, leather, so treated, will withstand-a temperature of 700 F. for a period of about 10 seconds without impairment, and a temperature of 600 F. fora period of about 20 seconds without impairment. At lower temperatures the times will be correspondingly longer.

The method of treatment herein, and particularly the heat treatment step is to be distinguished from prior methods :of treating grain leather wherein the same is subjected to elevated temperatures 'by the application to one or both sides thereof of a hot plate for the purpose of'contracting the pores and producing a much finer and closer grain. In the applicants method no pressure whatsoever is exerted onthe skin and the same is'freely suspended so that maximum overall shrinkage is obtained. In fact, it has been found that when leather is treated as herein disclosed, it is no longer subject to shrinkage by heat, regardless of the temperature, and will actually be destroyed by prolonged exposure to high temperatures before any further shrinkage will occur.

While I do not desire to be bound by any particular theory, it appears that the shrinkage, obtained by the heat treatment herein disclosed, serves to compact the finely divided particles of insulating material in a manner such as to increase their heat insulating characteristics. At the same time, the leather itself is compacted to further resist the passage of heat therethrough and to increase its resistance to the destructive efiects of high temperature heat. The overall elfect, as previously indicated, is to increase the heat resistance of the leather and to decrease its heat conductivity.

While a preferred embodiment of the invention has been disclosed herein, the invention is not to be construed as limited to the specific details illustrated and described except as included in the following claims.

I claim:

1. A method of dimensionally stabilizing unfabn'cated tanned leather containing solid particles of a material resistant to the transmission of heat, embedded in the pores thereof which comprises applying uniform heat to both sides of the leather While the leather is free of Contact with the heating means, the leather being held at temperatures of about 350 to 400 F. for from about minutes to 3 minutes.

2. The method of claim 1 wherein the leather is suspended to hang freely in a-heated atmosphere.

3. The method of claim 1 wherein the heat is applied by passing a stream of hot rapidly moving air over both faces of the leather.

4. The method as set forth in claim 1 wherein the finely divided material is diatomaceous earth.

5. The method as set forth in claim -1 wherein the finely divided'material is diatomaceous earth of a fineness such as to pass through a 600 mesh screen.

6. A dimensionally stabilized leather product comprising unfabricated tanned leather which has been impregnated with finely divided solid particles of a material resistant to the transmission of heat and then subjected to shrinkage by the uniform application of heat to both sides thereof while suspended to hang freely, at temperatures within the range of about 350 to 400 F. for periodsof about 15 minutes to 3 minutes. a

'7. Aleather product as set out in claim 6 wherein the impregnated leather is split leather from the flesh side of the hide.

8. A leather product as set forth in claim 7 wherein the finely divided material is diatomaceous earth.

9. A method for making a flexible shield .for Protec: tion against heat which method comprises providing a flexible fibrous and porous sheet-of a split type of leather, tumbling the sheet in a body of liquid containing a finely divided suspension of diatomaceous earth to cause the particles to become physically entangled within and throughout the interfibrous pores of the sheet, removing the liquid from the sheet thereby leaving the particles physically entangled within and throughout the thickness of the sheet, freely suspending the sheet in an oven, supplying heated air to the oven to maintain a temperature therein from about 350 F. to about 400 F., for a period of time from about three minutes .to about 15 minutes, and then removing the sheet from the oven.

References Cited in the file of this patent UNITED STATES PATENTS 2,272,935 Cotton Feb. 10, 1942 2,367,446 Strobino Jan. '16, 1945 2,444,347 Greger et al June 29, 1948 2,450,681 Muench Oct. 5, 1948 2,567,331 Gaiser et al Sept. 11, 1951 FOREIGN PATENTS 633,631 Great Britain Dec. 19, 1949 

1. A METHOD OF DIMENSIONALLY STABILIZING UNFABRICATED TANNED LEATHER CONTAINING SOLID PARTICLES OF A MATERIAL RESISTANT TO THE TRANSMISSION OF HEAT, EMBEDDED IN THE PORES THEREOF WHICH COMPRISES APPLYING UNIFORM HEAT TO BOTH SIDES OF THE LEATHER WHILE THE LEATHER IS FREE OF CONTACT WITH THE HEATING MEANS, THE LEATHER BEING HELD AT TEMPERATURES OF ABOUT 350* YO 400*F. FOR FORM ABOUT 15 MINUTES TO 3 MINUTES. 